About 40 million Chinese kids are taking piano lessons these days — and it’s all because of Lang Lang. The charismatic 27-year-old Chinese native — who was barely 18 when The Post made him a cover boy (“Lang Lang is hot hot hot”) — has been pretty busy. Maybe you caught him on “Sesame Street,” “Oprah” or the Beijing Olympics, where they sat him behind a ginormous white piano. Now the rock star of classical music is teaming with Wyclef Jean to help the children of Haiti.

“A few years ago, China had a huge earthquake and many children lost their lives, or their parents,” Lang Lang says. “I texted Wyclef right after I saw the news about Haiti. But the earthquake was two months ago, and I think people forget.” Lang Lang is determined they don’t. This week, iTunes released his recording of Chopin’s “Polonaise,” with proceeds going to Haiti releif. (Go to iTunes.com or text “HEROIC” to 839863 to download it.) Or catch him and Jean at Carnegie Hall for a benefit concert that includes an encore performance of “Gunpowder,” the piece they played at last year’s Nobel Prize ceremony. What’s that sound like? “He plays guitar and sings, and I play a lot of scales.” Don’t expect an album anytime soon: Lang Lang’s getting back to Beethoven. Sunday at 8:30 p.m., Tickets are $18 to $109 at Carnegie Hall, 57th Street at Seventh Avenue; 212-247-7800; carnegiehall.org.

— Barbara Hoffman

SHOW THEIR METAL

Metal fans have known Anvil since 1978 when they toured with bands such as AC/DC but never met with their contemporaries’ success. Then, just last year, film buffs came to know Anvil from the 2008 documentary “Anvil! The Story of Anvil,” which detailed the band’s tragically comic decades of coming up close in what, at times, plays out like a real-life “This Is Spinal Tap.” Tonight at the Gramercy Theatre, band and film come together at an 8 p.m. screening of Anvil’s movie, followed by a live performance from the band (along with a pair of opening acts). 127 E. 23rd St., at Lexington Avenue; (212) 614-6932. Tickets are $25 at livenation.com.

RUNAWAY STAR

If you still can’t get Michael Shannon’s Oscar-nominated performance in “Revolutionary Road” out of your head, you’re in luck. The actor, a dead-ringer for James Bond nemesis Jaws, is on the big screen again in “The Runaways” (he’s the band’s manager). But you can also catch him live onstage in the acclaimed off-Broadway revival of “Our Town” (Barrow Street Theatre, 27 Barrow St; 212-868-4444) as the Stage Manager.

“I always heard it was sentimental and hokey,” Shannon says of the play, which he had neither seen nor read. “It didn’t seem like it would be up my alley. But when I saw this production it rocked my world.” Although his profile has increased considerably since his Oscar nom, Shannon’s appearance in the play isn’t even being advertised. “I really like it that way,” he says. “I thrive on anonymity. I’m one of those lame actors who doesn’t enjoy the spotlight.” Even so, he’d better get used to it.

— Frank Scheck

ONCE IN A BLUE MOON

Bill Murray is a sardonic lunar tour guide and Dan Aykroyd a Holland Tunnel supervisor in the one-of-a-kind “Nothing Lasts Forever” (1984), which is having an extremely rare showing tomorrow at 92Y Tribeca. This charming, retro-futuristic fantasy stars Zach Galligan (“Gremlins’”) as a young aspiring artist who returns to a New York City despotically run by the Port Authority — until he’s dispatched to the moon by Father Knickerbocker (Sam Jaffee) to find his true love (Lauren Tom), meeting singer Eddie Fisher (playing himself) en route.

The semi-musical flick, shot mostly in black-and-white, has developed a substantial cult following, selling out earlier showings at Lincoln Center and BAM despite never having been released in any form in the United States. Director Tom Schiller, who says he was “inspired by every movie I’ve ever seen,” will introduce the feature and several short films he helmed for “Saturday Night Live,” including “Don’t Look Back in Anger” with John Belushi (who died before shooting his part for “Nothing Lasts Forever”). The theater is at 200 Hudson St., at Canal Street. Info: 92Y.org. More at nypost.com/blogs/movies.

— Lou Lumenick

KEEP ON TRUCKIN’

Some artists might swear cartoonist R. Crumb is God, and his Bible illustrations certainly won’t change their minds about the godfather of the underground comix style. Through April 17, the David Zwirner Gallery presents 207 works Crumb — who drew Fritz the Cat and Mr. Natural — created for “The Book of Genesis Illustrated by R. Crumb,” published last October. 519 W. 19th St., at 10th Avenue; 212-727-2070, davidzwirner.com.